In recent years, fluorescence detection devices have been used in a wide range of areas such as medical diagnoses based on quantitative change of, e.g., an enzyme where a disease is induced by, e.g., a proteolytic enzyme, environmental evaluations using an enzyme activity as a marker for, e.g., microorganisms existing in the environment, and monitoring operations in detection systems in which a fluorescence intensity is successively increased by a chemical reaction.
As an example of such fluorescence detection device, a fluorescence detection device has been proposed, which includes: a sample container that holds a sample; a container holding part that holds the sample container, the container holding part being capable of changing a temperature of the sample in the sample container; a fluorescence detector for measuring fluorescence from the sample; and a light source that emits excitation light for exciting a sample for fluorescence emission, wherein the light source and the container holding part, and the container holding part and the fluorescence detector are optically connected via respective optical fibers, and the optical fibers are installed in the container holding part so as to excite the sample in the container for fluorescence emission from the underneath of the sample container held by the container holding part and receive fluorescence emitted by the sample from the underneath of the sample container (see, for example, patent document 1). However, where excitation irradiation is performed from a bottom portion of a microtube such as an Eppendorf tube, the control in thickness and shape of the bottom portion cannot be considered sufficient because of the tube manufacturing process, resulting in wide optical variations.
For other examples, there have been proposed a fluorescence measurement device in which a liquid-state sample arranged at an excitation light converging position for an objective lens of an epi-illumination optical system using a fluorescent cube is held in a hole of a sample holding plate, the hole extending through the sample holding plate in parallel to an optical axis (see, for example, patent document 2); a fluorescence measurement device including a light source that emits excitation light, a sensor part that propagates the excitation light entered from an end thereof inside and emits evanescent light from another end thereof, and excites a fluorescent substance by the excitation light, the fluorescent substance indicating existence of a measurement target substance in a sample liquid in which the other end is immersed, and an photodetector that detects fluorescence emitted from the fluorescent substance by the excitation, wherein the sensor part includes a substantially-columnar sensor part body and a cylindrical cover portion surrounding the sensor part body via a space between an outer peripheral surface of the sensor part body at least adjacent to the other end and the cylindrical cover portion, and wherein the cover portion includes an occlusion portion that occludes the space at an end portion of the cover portion on the other end side (see, for example, patent document 3); an enzyme activity measurement device at least including a laser light source for near-infrared femtosecond laser light for inducing a process of multiphoton excitation of a substrate or a product of substrate metabolism, a radiation wave detection part that detects radiation wave generated from the process of multiphoton excitation of the substrate or the product of substrate metabolism; and an optical path that guides the near-infrared femtosecond laser light to a site where an enzyme exists and guides the radiation wave to the radiation wave detection part (see, for example, patent document 4); a fluorescence measurement device including a light source for exciting a fluorescence substance in a sample, a collecting lens that collects fluorescence emitted from the fluorescence substance, a spatial filter that transmits the fluorescence collected by the collecting lens, an photodetector that detects the fluorescence that has passed through the spatial filter, a signal analysis part that analyzes an output signal from the photodetector, and an adjustment part that adjusts an arrangement position of at least one of the collecting lens and the spatial filter based on an analysis result obtained by the signal analysis part (see, for example, patent document 5); and a fluorescence detection device including a white light source, an excitation-side light dispersion means for dispersing light emitted from the white light source, an excitation optical system including an image formation optical system not including an optical lens but consisting of a combination of mirrors, the excitation optical system irradiating with the light dispersed by the excitation-side light dispersion means a sample as excitation light, a fluorescence optical system including an image formation optical system not including an optical lens but consisting of a combination of mirrors, the fluorescence optical system collecting fluorescence emitted from the sample excited by the excitation light, a fluorescence-side dispersion means for dispersing the fluorescence collected by the fluorescence optical system, and a detector that detects the fluorescence dispersed by the fluorescence-side dispersion means (see, for example, patent document 6).
Meanwhile, as examples of periodontal disease-causing bacteria, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia are known, and these bacteria form a bacteria nest inside plaque (biofilm), causing inflammation at an interface between a tooth root and a gum, thereby ingesting blood components for reproduction. It is known that along with the inflammation, neutrophils infiltrate and as a result, the activity of, e.g., released leukocyte elastase increases. Based on such knowledge, test kits for analyzing a sample from a mouth cavity of a patient to detect the patient's periodontal disease have been proposed (see, for example, patent document 7). The test kit includes a first detection assay for detecting a first substance, which is Arg-gingipain derived from the bacterium P. gingivalis and a second detection assay for detecting a second substance, which is human neutrophil elastase derived from an immune system or an inflammation system of a patient.
Also, a sheet-like medical product for in vitro diagnosis has been commercially available, which detects β-naphthylamine liberated as a result of a BANA (N-benzoyl-DL-arginylβ-naphthylamido) substrate in a film with a sample applied thereto being degraded using a BANA degradative activity each of three types of bactertia, P. gingivalis, T. denticola and T. forsythia in subgingival plaque has, to check whether or not these bacteria exist.